It is most likely to be something in your crystallisation condition,
your cryoprotectant, or the buffer you stored your protein in.
Could be a detergent carried through several steps of purification
Could for example be some part of a PEG molecule that gets ordered round
a more hydrophobic bit of your protein surface.
You need to think about everything your protein has come into contact
with, possibly even inside the cell. It is not uncommon to carry
cofactors right through a purification, less likely in something more
surface bound like this.
Best wishes
Nick
--
Prof Nicholas H. Keep
Executive Dean of School of Science
Professor of Biomolecular Science
Crystallography, Institute for Structural and Molecular Biology,
Department of Biological Sciences
Birkbeck, University of London,
Malet Street,
Bloomsbury
LONDON
WC1E 7HX
email [log in to unmask]
Telephone 020-7631-6852 (Room G54a Office)
020-7631-6800 (Department Office)
Fax 020-7631-6803
If you want to access me in person you have to come to the
crystallography entrance
and ring me or the department office from the internal phone by the door
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